As an oversimplification, RSA works by taking two huge prime numbers (the private key) and multiplying them together (the public key). You could get the private key by factoring the public key but the best way to factor a prime number is to basically just try every combination with a few tricks sprinkled in until something works which could take millions of years with modern computers. You can hoard everyone’s public key until computers can crack it in a reasonable amount of time but everyone involved will be long gone by then.

The whole point of private and public keys is to have an operation that’s easy to do one way but would take so long to reverse that it’s virtually impossible. There’s nothing stopping you trying except the time and effort involved.

Yeah, I’d say not cheaping out on floss is one of the more important things. I bought some cheap floss while on a trip since I forgot mine and it absolutely destroyed my gums even though I’ve been flossing for years without any issues.

That’s why you use virtual cards for services that you aren’t sure you want to renew and have them lock automatically right before they do. Better yet, use virtual cards everywhere you can.